Question

What method would you choose to solve the equation 2x2 – 7 = 9? Explain why you chose this method.

Answer 1

Normal solution;
By taking -7 to the RHS, you will have 
$2 x^{2} =16$
dividing both sides by 2 gives;
$x^{2} =8 x= \sqrt{8} x=2 \sqrt{2}$

Answer 2

This is a quadratic equation . We order to equate to zero

2x² – 7 = 9  
 
2x² - 7-9 = 0
2x² - 16 = 0

This equation is a binomial
2* (x² - 8) = 0
We choose the simplest method . The equation with practice it can be calculated in the memory

The product is equal to 0 if one of the factors is zero

2≠0  ∨     x² - 8 = 0
               x² = √8
               x = √8     ∨  x= - √8

Answer : x = √8 ∨ x = -√8